There are radio modules which communicate with one another by radio, i.e. in wireless manner. So that the radio modules are able to communicate with each other, the respective address of the other radio module must be known or must be detectable by radio.
For safety reasons, for instance for offering protection against attacks per DoS (Denial of Service), the radio modules—at least for most of the time—should be “invisible” or not detectable for other radio modules with which a communication is not desired.
This can be solved in that the address of the communication partner is already known, because it is stored for instance in the radio module which desires to communicate with the communication partner. This, however, is not feasible if the modules (frequently) or units in which they are installed have to be replaced or if a pool made up of many modules or units is used and the communication partner from the pool is not known in advance.
Another solution is to “uncover” a module or unit, for instance by pressing a button on the respective module or unit (e.g. activating a “visibility” mode). This is cumbersome, as it requires a corresponding action by a user. What is more, this generates additional costs for corresponding external switches.
Especially in case of units which are spatially separated and/or firmly mounted (e.g. ceiling installation), so that the user does not have any possibility of intervention, there is no possibility that these modules which are unknown to each other enter into a communication connection.
There are various known radio techniques with differing properties in terms of data throughput, data transmission rate, range, frequency, channels etc. These techniques include, but not exclusively, Z-Wave, battery-less radio sensory systems by EnOcean, Zigbee, Bluetooth, WiFi (802.11a, 802.11b, etc.), WUSB (wireless USB), WHDI (SRI) as well as WiHD (wireless HDMI) and proprietary solutions. In the field of medical engineering, for instance, specific radio standards have established themselves, including in particular Bluetooth, Zigbee and WiFi.
“Bluetooth” is generally subdivided in “Classic” and “Low Energy”. “Classic” relates to the original protocols Bluetooth 3.0, Bluetooth 2.1 . . . , whose modules or chips are also referred to as classic module. Since Bluetooth 4.0 there is also the option of “Low Energy” (additional protocol stack to “Classic”) which allows an energy-saving mode of operation in an economical way due to a quick establishment of the connection. However, relevant Bluetooth-based low-energy modules only achieve a lower data transmission rate and a lower data throughput. All Bluetooth-4.0 modules which are available on the market are based solely on the classic protocol or solely on the low-energy protocol, so-called single-mode modules, or are based on both protocols, so-called dual-mode modules which allow to switch over between the classic mode and the low-energy mode. However, even such a dual-mode module has a higher energy consumption than a single-mode module in the activated state before the establishment of a connection, as the energy consumption prior to the establishment of a connection is determined by the classic mode.
In accordance with the Bluetooth protocol, there is e.g. the “discoverable” mode in which the module looks for other Bluetooth modules and is receptive to requests from other Bluetooth modules. Further, there is the “connectable” mode in which the module, if it is addressed with its address, is ready for entering into a connection, but itself cannot be detected by other modules.
A low-energy module has the special characteristic that it can establish and maintain only one connection to another (low-energy) module at a time.
There are some orthopedic units which are supplied with voltage by a battery or an accumulator and perform their communication per radio.
In addition, an orthopedic navigation system is known which serves the physician as a smart tool with joint-surgical interventions such as e.g. for the patient-specific positioning of implants in the field of endoprosthetics. In this context, the position of infrared light sources (passive, infrared light reflecting transmitters) which are attached for instance to the body of the patient, are intraoperatively detected in space by means of a video-optical camera system. It is possible to calculate the location and the position of the infrared light reflecting transmitters relative to one another and also the location and position of the surgical instruments relative to the patient. The measured values are computed with further data (for example with pre-operative planning data) and are supportive in placing and positioning the implant. Moreover, the individual implant components can be matched with each other in order to ensure the durability and function of the implant by optimum alignment.
However, if it should happen that during a surgical procedure the camera has to communicate with the computation/display device in wireless fashion by radio, a higher data throughput (and a higher data rate) is frequently required for each radio path, exceeding 500 kbit/s, for example. Thus, there is the need to employ radio techniques which usually do not only offer a higher data rate, but also have a higher power consumption. The power consumption during use, however, is not necessarily the greatest problem; rather, the problem is the standby current during the time in which a unit or the corresponding radio module is on standby for entering into a connection or is waiting for a connection request. This has an influence on the service life of the battery-powered or accumulator-powered units if these are to be always ready for entering into a connection.